1. Field of the Invention
The present invention relates to a recording apparatus comprising means for preventing a recording paper from coming in contact with a recording head even if the recording paper lifts up due to the ejection of ink thereon or a paper with a propensity to curl is used.
2. Description of the Related Art
Inkjet recording apparatuses for carrying out a recording operation by ejecting ink onto the recording face of a recording paper are widely used. Such a recording apparatus generally comprises a recording head with an ink ejection aperture forming surface for ejecting ink onto the recording face of a recording paper.
For instance, a recording head ejects ink droplets controlled based on a drive control signal supplied according to image data and formed either by the pressure of an electro-mechanical conversion body or the thermal energy of an electro-thermal conversion body toward the recording surface of a recording paper through the ink ejection aperture forming surface.
And, in an attempt to speed up a recording speed, there are relatively high density recording heads formed in a matrix between 300 dpi and 600 dpi for example and so called multi-nozzle, wide recording heads on which ink ejection apertures are formed across the entire recording width of a recording paper, for instance the entire width of the recording paper. Incidentally, in order to place a recording head over the entire area of recording, a structure placing a plurality of recording heads with a recording range which is equivalent to “a few tenths” of the entire recording width. In such a case, the adopted system is for securing a recording range without a gap across the entire recording range by placing a plurality of recording heads in a zigzag pattern, in order to make the recording range continuous.
Meanwhile, in order to make a recording apparatus full color, four color recording heads, i.e., CMYK (cyan, magenta, yellow, and black respectively), need to be arranged serially in the transport direction of a recording paper. This results in the recording head area becoming wide in the direction of the recording paper transport. In such a recording apparatus, the distance between the recording face of a recording paper and the ink ejection forming face must be continuously maintained at a predetermined value in order to maintain a stable recording.
The recording surface of a recording paper, however, sometimes lifts-up due to a wrinkle, curl or waviness caused by an absorption and subsequent evaporation of moisture, and further to a wrinkle or waviness, the so called cockling phenomenon, caused by the absorption of ink. Due to this, the recording paper comes into contact with the recording head, bringing about problems such as contamination of the recording head, recording head nozzle clogging, degradation of print quality, et cetera.
As countermeasures to such issues, methods have been proposed for avoiding a lift-up of recording paper, such as the one for holding down a recording paper by a hold-down member in an upstream part of the recording paper transport path, the one for maintaining flatness by sucking air through small holes in a platen member having a plurality of small holes to keep the recording surface of a recording paper close to the platen, and the one for transporting a recording paper electro-statically attached to the transport belt.
And, a laid-open Japanese patent application publication No. 2001-293919 has disclosed a method for preventing a sheet from coming in contact with a recording head by the equipping of a hold-down roller on an edge part of a carriage to which is mounted a recording head in order to constrain a sheet from lifting-up.
In the meantime, a laid-open Japanese patent application publication No. 2001-26154 has disclosed a paper hold-down mechanisms corresponding to each of recording heads placed in a plurality of columns in the direction of the recording paper transport.